Discovery of Tin

Tin has been known since ancient times. We do not know who discovered it.

The Bronze Age began in about 3000 BC and tin was used in bronze, which contains roughly ninety percent copper and ten percent tin.

The addition of tin to bronze alloys improves their properties compared with pure copper: for example, bronze is harder and more easily cast than copper.

The ancient Greeks obtained their tin by sea-trade and referred to the source as ‘The Cassiterides’, meaning Tin Islands.

These islands were most likely to have been in Cornwall, Great Britain and/or north-west Iberia, Spain where there are large tin deposits.

In less ancient times, British scientist Robert Boyle published a description of his experiments on the oxidation of tin in 1673.

Tin’s chemical symbol, Sn, comes from its Latin name, ‘stannum.’

Time lapse movie of tin’s allotropes. Metallic white tin becomes non-metallic gray tin. This is known as ‘tin pest’ and is a problem at low temperatures. 1 second of movie equals one hour in real time.

A piece of zinc metal in tin chloride solution. Zinc is more reactive than tin, so zinc chloride forms, replacing the tin chloride. Crystals of pure metallic tin begin to form on the zinc.

Solder can be used to secure electronic components. Solder is usually about 60% tin and 40% lead. Here solder is being removed from a circuit board. Image by Hugo.

Appearance and Characteristics

Harmful effects:

Tin is considered to be non-toxic but most tin salts are toxic. The inorganic salts are caustic but of low toxicity. Organometallic compounds of tin are highly toxic.

Characteristics:

Tin is a silvery-white, soft, malleable metal that can be highly polished.

Tin has a highly crystalline structure and when a tin bar is bent, a ‘tin cry’ is heard, due to the breaking of these crystals.

In compounds tin is usually in the divalent state (Sn2+) or tetravalent state (Sn4+).

It resists oxygen and water but dissolves in acids and bases. Exposed surfaces form an oxide film. When heated in air, tin forms tin(IV) oxide (stannic oxide) which is feebly acidic.

Tin has two allotropic forms at normal pressure, gray tin and white tin. Pure white tin slowly tends to become the gray powder (gray tin), a change commonly called ‘tin pest’ at temperatures below 13.2 oC. Gray tin has no metallic properties at all. Commercial quality tins are resistant to tin pest as a result of the inhibiting effects of minor impurities.

Uses of Tin

Tin is used as a coating on the surface of other metals to prevent corrosion. ‘Tin’ cans, for example, are made of tin-coated steel.

Tin can be rolled into thin foil sheets (tinfoil). Present day ‘tinfoil’ to cover or wrap food is usually made from aluminum.

Alloys of tin are commercially important in, for example, soft solder, pewter, bronze and phosphor bronze.

Tin chloride (stannous chloride, SnCl2) is used as a mordant in dyeing textiles and for increasing the weight of silk.

Stannous fluoride (SnF2) is used in some toothpastes.

Abundance and Isotopes

Abundance earth’s crust: 2.3 parts per million by weight, 0.4 parts per million by moles